Compacted parts made from insulated iron powders are a convenient alternative to lamination steels in alternating current (AC) applications. Traditionally, compacted parts for powder metal electromagnetic alternating current applications are manufactured using compaction pressures as high as 1600-2000 MPa in order to achieve a high density of the resulting green compacted part. These high compaction forces oftentimes damage the mechanical parts of the compaction device, particularly those used to make parts with complex geometries.
To achieve higher densities in powder metal parts for non-electromagnetic AC applications, the green compact is heated at temperatures in excess of 650° C. in order to remove the lubricant, followed by recompaction at compaction pressures of 600-800 MPa. Higher densities are thus by achieved by re-compacting metal to fill all the voids left by the eliminated lubricant.
For electromagnetic AC applications, however, a coating is typically applied on the metal powder to eliminate metal-to-metal contact. These coatings cannot withstand the excessive temperatures typically used for lubricant removal.
As such, what are needed are compaction methods for insulated powders that use lower compaction pressures and lower lubricant-removal temperatures, while maintaining high densities of the compacted part.